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/****************************************************************************** |
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* Top contributors (to current version): |
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* Andrew Reynolds, Aina Niemetz |
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* |
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* This file is part of the cvc5 project. |
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* |
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* Copyright (c) 2009-2021 by the authors listed in the file AUTHORS |
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* in the top-level source directory and their institutional affiliations. |
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* All rights reserved. See the file COPYING in the top-level source |
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* directory for licensing information. |
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* **************************************************************************** |
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* |
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* Arrays skolem cache. |
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*/ |
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#include "theory/arrays/skolem_cache.h" |
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#include "expr/attribute.h" |
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#include "expr/bound_var_manager.h" |
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#include "expr/skolem_manager.h" |
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#include "expr/type_node.h" |
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using namespace cvc5::kind; |
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namespace cvc5 { |
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namespace theory { |
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namespace arrays { |
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/** |
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* A bound variable corresponding to an index for witnessing the satisfiability |
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* of array disequalities. |
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*/ |
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struct ExtIndexVarAttributeId |
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{ |
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}; |
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typedef expr::Attribute<ExtIndexVarAttributeId, Node> ExtIndexVarAttribute; |
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SkolemCache::SkolemCache() {} |
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Node SkolemCache::getExtIndexSkolem(Node deq) |
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{ |
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Assert(deq.getKind() == NOT && deq[0].getKind() == EQUAL); |
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Node a = deq[0][0]; |
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Node b = deq[0][1]; |
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Assert(a.getType().isArray()); |
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Assert(b.getType() == a.getType()); |
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NodeManager* nm = NodeManager::currentNM(); |
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// get the reference index, which notice is deterministic for a, b in the |
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// lifetime of the node manager |
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Node x = getExtIndexVar(deq); |
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// make the axiom for x |
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Node as = nm->mkNode(SELECT, a, x); |
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Node bs = nm->mkNode(SELECT, b, x); |
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Node deqIndex = as.eqNode(bs).notNode(); |
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Node axiom = nm->mkNode(IMPLIES, deq, deqIndex); |
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// make the skolem that witnesses the above axiom |
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SkolemManager* sm = nm->getSkolemManager(); |
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return sm->mkSkolem( |
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x, |
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axiom, |
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"array_ext_index", |
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"an extensional lemma index variable from the theory of arrays"); |
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} |
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Node SkolemCache::getExtIndexVar(Node deq) |
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{ |
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Node a = deq[0][0]; |
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TypeNode atn = a.getType(); |
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Assert(atn.isArray()); |
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Assert(atn == deq[0][1].getType()); |
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TypeNode atnIndex = atn.getArrayIndexType(); |
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BoundVarManager* bvm = NodeManager::currentNM()->getBoundVarManager(); |
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return bvm->mkBoundVar<ExtIndexVarAttribute>(deq, atnIndex); |
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} |
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} // namespace arrays |
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} // namespace theory |
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} // namespace cvc5 |